Study guide: The Digestive System biop1 organisation

📋 Course Outline

1. Cells, Tissues, Organs and Systems
2. Food Nutrients and Digestion
3. Digestion in the Mouth and Stomach
4. Accessory Organs and Small Intestine
5. Absorption and Use of Digestion Products

📖 1. Cells, Tissues, Organs and Systems

🔑 Key Concepts & Definitions

• Tissue: A group of cells with a similar structure and function.
• Organ: A group of tissues working together for a specific function.
• Organ system: A group of organs that work together to form an organism.

📝 Essential Points

• Muscle cells contract because they contain protein fibres that can change length, and their many mitochondria provide the energy needed for contraction.

• The stomach is an organ containing muscle tissue and glandular tissue, which releases enzymes.

💡 Memory Hook

Cells build tissues, tissues build organs, and organs form systems.

📖 2. Food Nutrients and Digestion

📝 Essential Points

• The three main nutrients in food are:

  • carbohydrates such as starch
  • protein
  • lipids, also called fats

• Carbohydrates, proteins and lipids are large molecules that are too large to be absorbed into the bloodstream without digestion.

• During digestion, enzymes break large food molecules into smaller molecules that can then be absorbed into the bloodstream.

💡 Memory Hook

Large molecules need digestion; small molecules can be absorbed.

📖 3. Digestion in the Mouth and Stomach

★ Must-know

• In the mouth, chewing breaks food into smaller pieces and enzymes in saliva begin digesting starch into smaller sugar molecules.

• In the stomach, enzymes begin the digestion of proteins, and hydrochloric acid helps those enzymes digest proteins.

• Stomach muscle churning turns food into a fluid, increasing the surface area available for enzyme digestion.

Further detail

• After the mouth, food passes down the oesophagus into the stomach.

• Food spends several hours in the stomach before the resulting fluid passes into the small intestine.

📖 4. Accessory Organs and Small Intestine

★ Must-know

• The liver releases bile into the small intestine, where bile speeds up lipid digestion and neutralizes acid released from the stomach.

• The pancreas releases enzymes into the small intestine that continue starch and protein digestion and begin lipid digestion.

• As the fluid moves through the small intestine, digestion produces small food molecules that are absorbed into the bloodstream by diffusion or active transport.

Further detail

• The walls of the small intestine release enzymes that continue the digestion of proteins and lipids.

• The fluid passes from the stomach into the small intestine, where chemicals are released from the liver and pancreas.

📖 5. Absorption and Use of Digestion Products

★ Must-know

• In the small intestine, small molecules produced by digestion enter the bloodstream by diffusion or active transport.

• As the remaining fluid passes through the large intestine, water is absorbed into the bloodstream.

• The body uses products of digestion to build new carbohydrates, lipids and proteins.

Further detail

• Feces are released from the body at the end of the digestive process.

• Some of the glucose produced by digestion is used in respiration.